package com.zhang.respose;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;

public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.要获取下载文件的路径
//        String realPath = this.getServletContext().getRealPath("/tank.jpg");
//        D:\soft\apache-tomcat-9.0.54-windows-x64\apache-tomcat-9.0.54\webapps\response_war\tank.jpg
        String realPath = "D:\\goodgoodStudy\\codes\\javaweb-servlet\\response\\target\\classes\\tank.jpg";
        System.out.println("获取下载文件的路径"+realPath);
        //2.下载的文件名是啥?
        String filename = realPath.substring(realPath.lastIndexOf("\\") + 1);
        //3.设置想办法让浏览器能够支持下载我们需要的东西
        resp.setHeader("Content-Disposition","attachment;filename"+ filename);
        // 4.获取下载文件的输入流
        FileInputStream in = new FileInputStream(realPath);
        //5.创建缓冲区
        int len = 0;
        byte[] buffer = new byte[1024];
        //6.获取OutputStream对象
        ServletOutputStream outputStream = resp.getOutputStream();
        //7.将FileOutputStream流写入到buffer缓冲区
        //8.使用OutputStream将缓冲区中的数据输出到客户端!
        while ((len=in.read(buffer)) > 0){
            outputStream.write(buffer,0,len);
        }

        in.close();
        outputStream.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}
